The demons in the Dororo anime, often referred to as majin or demon gods, are a group of supernatural entities that serve as the primary antagonistic force driving the narrative. Their origin is tied directly to the desperation of a feudal lord, Daigo Kagemitsu, who, during the war-torn Sengoku period, makes a pact with them to save his dying lands. In the 2019 anime adaptation, there are twelve of these powerful beings, a change from the original manga where there were forty-eight.

These demons are motivated by a transactional hunger for human existence. They agreed to take the body of Kagemitsu's unborn son, Hyakkimaru, piece by piece. In return for this sacrifice, they ensured that the Daigo family's territory would flourish, bringing prosperity and power to the lord. They are not a unified army but rather individual creatures, each possessing a specific stolen part of Hyakkimaru, ranging from his skin and nervous system to his limbs, ears, voice, and eyes. Because the pact was made with them, they are intrinsically linked to the fate of the Daigo domain; as long as they hold Hyakkimaru's body parts, the land remains prosperous.

Their role in the story is fundamentally that of a goal and an obstacle for the protagonist, Hyakkimaru. Driven by a primal need to feel whole and human, Hyakkimaru hunts these demons across the countryside. Each demon he slays releases the body part it held, allowing it to regrow or manifest on his artificial form. This act of killing is a double-edged sword, as each demon's death chips away at the prosperity of the land, creating a moral conflict between Hyakkimaru’s personal quest for humanity and the collective good of the people living under his father's rule. The demons force this question throughout the series: is the return of one man's body worth the potential suffering of many?

In terms of personality and abilities, the demons are far from a monolithic evil. They are incredibly diverse, each embodying different aspects of malice, nature, or human fear. Some, like the first demon Deiki, are mindless, grotesque blobs of muck, acting on pure predatory instinct. Others, like Bandai, are cunning and manipulative, taking the form of a beautiful woman to lure and devour travelers. A demon named Nihiru manifests not as a monster, but as a cursed sword that drives its wielder to kill. Their abilities are as varied as their forms, from controlling insects to altering perceptions.

However, a key development in the narrative reveals that not all demons are purely evil. A striking exception is the Jorogumo, a spider demon who, despite needing to feed on human life force, forms a genuine, consensual bond with a human man. Hyakkimaru, whose supernatural sight allows him to see the essence of beings, ultimately spares her because she does not register as an enemy. This moment introduces significant nuance, suggesting that the line between demon and human is not always clear and that coexistence might be possible. This grey area is further explored as Hyakkimaru himself, in his single-minded quest and with his prosthetic body, is often mistaken for a demon by frightened villagers, blurring the identity of the hunter and the hunted. The demons represent more than just monsters; they are the physical embodiment of a cursed contract, a measure of a man's humanity, and the price of a prosperity built on a broken foundation.